1. Field of the Invention
The present invention relates to a sheet binding processing apparatus for crimp-binding a sheet bundle, a sheet post-processing apparatus having the sheet binding processing apparatus, and an image forming system having the sheet post-processing apparatus.
2. Description of the Related Art
A sheet post-processing apparatus having a sheet binding processing apparatus that receives sheets, on which images are formed by an image forming apparatus, on a processing tray and applies binding processing to the sheet bundle on the processing tray has heretofore been known.
Among such binding apparatuses, a sheet binding processing apparatus that can apply binding processing to a sheet bundle without using a metal staple, by crimping the sheet bundle to cause entanglement of fibers of the sheets, has been provided in recent years . Such crimp binding is configured so that the sheet bundle is bound by making crimping teeth firmly bite the sheet bundle to crimp the sheets together. The crimp teeth are a pair of crimping members having a recessed and protruded shape formed by alternately arranging a plurality of recesses and a plurality of protrusions in parallel. Such crimp binding has an advantage that the sheets can be easily exfoliated and separated since the sheets are bound without passing a metal staple.
The crimp binding of sandwiching the sheets between the upper and lower protrusions and recesses can break the sheets because of the biting of the protrusions into the recesses. The biasing force for crimping is thus difficult to control. A binding apparatus has therefore been proposed in which a pair of crimping members each include protrusion (recess) of which a top (bottom) is a surface parallel to a sheet surface of a sheet, and a side surface of the protrusion (recess) is a slope tilted with respect to the sheet surface, so that if the protrusions and recesses of the pair of crimping members mesh with each other, the slopes make contact with each other and a gap is formed both between the top of the protrusion of one of the crimping members and the bottom of the recess of the other crimping member and between the top of the protrusion of the other crimping member and the bottom of the recess of the one crimping member, whereby breakage of the sheets is prevented (for example, JP2015-054490A).